Stabilized compositions comprising monomeric 1, 1-dicyano ethylene



Patented Jan. 1954 SIITIONISCOMPRISING MONOMERIG 1,1-DICYANO ETHYLENEAlan E; Ardis, Ciiyahoga Falls, Ohio, assignor to STABILIZED COMPO The'B. F. Goodrich Company, New York, N. Y.,

a corporation of New York No Drawin Ap lication-May 7, 1952, Serial No.286 600 5 Claims, (Cl. ZED-465.8)

This invention relates to stabilized composi tions comprising monomericvinylidene cyanide and pertains more particularly to compositionscomprising the crude product containing monomeric 1,1"- dicyano ethylenewhich is obtained by pyrolyzing 1-acetoXy=l,l-dicyano ethane, and alsocomprising a dialkyl sulfate as a stabilizer for the momomeric1-,l*-dicyano ethylene.

It is disclosed in U.- S. Patent 2,476,270, that monomeric 1,1-'dicyanoethylene can be obtained by pyrolytic decomposition at temperatures ofabout 400 C; to 750 C. of 1=acetoxy-1-,-1=dicyano ethane (also known ascliacetyl cyanide) followed by separation of the monomeric LI-dicyanoethylene from the pyrolysis product. The mono meric 1,1-dicya'1ioethylene "as thus obtained in relatively pure form is a remarkablemonomer which can be polymerized, either alone or with otherpolymerizable monomers in a non-ionic medium to give homopolymers andinterpolymers which can be utilized to form extremely valuablefilaments, films, shaped articles and the like.

The pyrolysis of 1-acetoxy-Ll-dicyano ethane proceeds substantially asfollows:

However, it has been observed in carrying out this reaction on a pilotplant or commercial scale, that the 'l-ac'etoxy- Ll-dicyano e'th'ai'n'eis not completely cracked pyrolytically to 1,1-dicyano ethylene andacetic acid; rather, there are several other unidentified products inthe product resulting from {the pyrolysis reaction;

It has been further observed that one or more or the unidentifiedproducts catalyzes the ionic polymerization of the 1,1-dicyano ethylenemonomer, so that the 1-acetoxy-1,1-dicyano etlia'n'e pyrolysis productis ordinarily an inherently unstable material, and in the absence of astabilizer (or even in the presence of certain know stabilizers} themonomeric LI-d-icy'ai m ethylene present in the pyrolysis productr'apidly polymerizes ionically to form a low molecular weight1,1-dicyano ethylene polymer that is of little or no value as such. Thispolymer can be separated from the remaining constituents in thepyrolysis product and then depolymerized to give the monomeric1,1-dicyano ethylene in fairly pure form, as disclosed in U. S. Patent2,535,827, but such a series of operations is obviously not desirablefrom the standpoint of efficiency and economy in a commercial plant.

Accordingly, it is an object of the present in vention to providematerials which will efiectively stabilize crude monomeric 1,1-dicyanoethyleneagainst ionic polymerization and will inhibit the activity ofany deleterious polymerization catalyst which may be present in thecrude l-acetoxy-1,l-dicyano ethane pyrolysis product. It is anotherobject of this invention to provide stabilized compositions containingthe l-acetoxy-Ll-dicyano ethane pyrolysis product, in which compositionsthe 1,1-dicyano ethylene present remains in the monomeric form forextended periods of time, and which can be used as such, without thenecessity for separation and purification of the monomeric 1,1-dicyanoethyL- ene, in preparing useful polymers and interpolymers of1,1-dicyano ethylene. Other objects will be apparent from thedescription which follows.

It has now been discovered that the above and other objects are attainedby stabilizing crude monomeric 1,1-dicyano ethylene, and particularlythe crude pyrolysis product of l-acetoxy- Ll-dicyano ethane, with adialkyl sulfate. In this manner, compositions are obtained in which theLl-dicyano ethylene remains in the mono-'- meric form for relativelylong periods of time. It thus becomes possible to store the L-acetoxy--1,l'-dicyano ethane pyrolysis product before using it. It also becomespossible to utilize such compositions in polymerization recipes and toobtain a useful high molecular polymer or interpolymer of 1,1-dicyanoethylene, rather than the low molecular polymer obtained when nostabilizer is utilized to inhibit the catalytic efiect of theunidentified products in the pyrolysis mixture.

It is quite surprising that the dialkyl sulfates, which are esters,should act as stabilizers to prevent the ionic homopolymerization ofmonomeric 1,1-dicya'no ethylene since many esters have the exactlyopposite effect. For example 1,1-dicyano ethylene monomer polymerizesquite rapidly in the presence of trialkyl phosphates.

The dialkyl sulfates utilized as stabilizers according to this inventioninclude *clim'ethyl suliate, diethyl sulfate, methyl ethyl sulfate,-di-npropyl sulfate, di-isopropyl sulfate, di-n-butyl sulfate, diamylsulfate, dioctyl sulfates and the like all of which possess thestructure wherein each R represents an alkyl group preferably containingfrom 1 to 8 carbon atoms.

No special procedures are necessary in preparing the compositions ofthis invention. For example, they may be prepared simply by placing thedi-alkyl sulfate in the receiver in which the lacetoxyl,1-dicyano ethanepyrolysis product 100 C. and the time required for polymerization of themonomeric 1,1-dicyano ethylene, is evidenced by formation of anon-flowing gel, and called the gel time, is observed. The results areshown in the following table:

is condensed and collected. A more desirable expedient, however,consists in spraying the stabilizer into the condensing pyrolysisproduct as the latter enters the receiver, thus assuring more rapid andeffective contact of stabilizer with pyrolysis product. Also, thestabilizer may be incorporated in a quench liquid if such is utilized tocondense the pyrolysis product vapors, as disclosed in copendingapplication Serial No. 286,496, filed May 7, 1952, or if desired, thestabilizer may even be added to the 1-acetoxy-1,1- dicyano ethane beforeits pyrolysis, in which event it is carried over into the pyrolysisproduct.

Any desired quantity of stabilizer may be utilized, although the optimumamount varies slightly with each batch of pyrolysis product, probablybecause of the diiierent degree of lacetoxy-l,1-dicyano ethanedecomposition obtained from run to run. In general, however,

only small quantities of the order of about 0.01%

to 1 or 2% by weight (based on the weight of the pyrolysis product) aredesirably utilized, although amounts as high as 5 or by weight or evenhigher may be employed, if desired. Large amounts of stabilizer are notpreferably utilized, however, both for reasons of economy as well asbecause of the fact that the stability tends to drop off slightly whenlarge amounts of the dialkyl sulfates are present, although suchcompositions do remain stable for a considerably longer period of timethan pyrolysis products containing no stabilizer.

The following examples are intended to illustrate the unusual stabilitypossessed by the novel compositions of this invention. They are not,

however, to be construed as a limitation upon the scope thereof, forthere are numerous possible variations and modifications.

Examples I to IV unidentified products. The products treated with 0dialkyl sulfate, and a control, are maintained at In all of the aboveexamples the product remained stable for more than 165 minutes whereasin the control product the 1,1-dicyano ethylene had polymerized in '70minutes. By visual observation it was determined that the products ofExample I was more stable than the product of Example II or 111 thusindicating that the lower stabilizer concentration is more effective.

The above examples have been concerned with stabilizing crude monomeric1,1-dicyano ethylene obtained by the pyrolysis of 1-acetoxy-1,1-dicyanoethane. However, the crude monomer produced in other ways often containsimpurities which cause it to polymerize by an ionic mechanism and thepresence of the stabilizers of this invention is effective in preventingsuch polymerization. Accordingly, the invention is not limited to anyparticular process for securing crude unstable monomeric 1,1-dicyanoethylene.

It is also to be understood that the examples are not intended otherwiseto limit the invention, since variations and modifications therein arewithin the spirit and scope of the appended claims.

I claim:

1. A composition comprising crude unstable monomeric 1,1-dicyanoethylene and, as a stabilizer therefor, a dialkyl sulfate present in aconcentration of about 0.001% to about 10.0% by weight.

2. A composition comprising monomeric 1,1- dicyano ethylene, acetic acidand other substances resulting from the pyrolysis of l-acetoxy-1,1-dicyano ethane, and as a stabilizer therefor, a dialkyl sulfatepresent in a concentration of about 0.001% to about 10.0% by weight.

3. A composition according to claim 2 wherein the stabilizer is presentin a concentration of 0.01 to 2% by weight.

4. A composition according to claim 3 wherein the stabilizer is dimethylsulfate.

5. A composition according to claim 4 wherein the stabilizer is diethylsulfate.

ALAN E. ARDIS.

Name Date Ardis July 19, 1949 Ardis et al. Dec. 26, 1950 Number

1. A COMPOSITION COMPRISING CRUDE UNSTABLE MONOMERIC 1,1-DICYANOETHYLENE AND, AS A STABILIZER THEREFOR, A DIALKYL SULFATE PRESENT IN ACONCENTRATION OF ABOUT 0.001% TO ABOUT 10.0% BY WEIGHT.